Closure for air evacuated container

ABSTRACT

The disclosure is of a novel closure for air evacuated tubular containers and comprises a tubular body having flexible, elastic sidewalls, an open end, a closed end formed by a cannula-pierceable, flexible, elastic end wall having a concavo-convex configuration in cross-section and a flange disposed radially about the periphery of the open end. The novel closure structure takes advantage of the vacuum force in the container to maintain a gas-proof, hermetic seal, reduces the thickness required of the closure to maintain the hermetic seal and is easier to assemble in an air evacuated container. The disclosure is also of a novel method of assembling the closure of the invention in an air evacuated tubular container.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of U.S. application Ser. No. 663,921filed Mar. 4, 1976 and now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns closures for containers and more particularlyconcerns gas-proof, cannula penetrable, self-sealing closures fortubular vacuum holding containers.

2. Brief Description of the Prior Art

The prior art is replete with descriptions of closure members forcontainers including air evacuated vacuum holding containers; see forexample U.S. Pat. Nos. 2,334,905; 3,106,206; 3,136,440; 3,313,439;3,330,282; 3,460,702; and 3,653,528.

In spite of the highly developed state of the art, closure members forair evacuated containers have many inadequate features and the perfectclosure has yet to be developed. For example, in the medical, biologicaland laboratory fields, sealed vacuum holding tubular containers arefrequently provided having cannula pierceable, self-sealing,elastomeric, gas-proof closures whereby entry into the container may beobtained by means of a needle so that fluids may be inserted orwithdrawn without breaking the sterility of the container. After theneedle is removed from the closure, the closure immediately reseals thepierced entry. One type of closure member frequently used with airevacuated containers is an elastomeric plug having an enlarged headportion and recesses in upper and lower portions to provide a cannulapenetrable zone; see for example FIG. 4 of U.S. Pat. Nos. 3,136,440 and3,106,206. In general, the prior art closure members for vacuum holdingtubular containers are relatively thick, relatively inflexible andrequire relatively high forces for insertion in the open end of an airevacuated tubular container.

The closure member of my invention is an improvement over the prior artclosures in that it requires less material (about 30% by weight less)for construction, without a sacrifice of gas-proofing or vacuum holdingcapacity. Having less bulk and lighter construction, the closure memberof my invention is less costly to produce, is easier to assemble in theair evacuated container and requires a much lower force to penetratewith a needle. The latter is particularly advantageous to a moreefficient utilization of the container assembly by the consumer.

The structure of my novel closure member also provides for a novelmethod of inserting an elastomeric closure into an air evacuated tubularcontainer. Prior hereto, such assembly has required considerable forceto make the insertion. By the method of my invention, less force isrequired to insert and assemble the closure member of an air evacuatedtubular container. This of course is advantageous in that there is lesshazard and a reduction in breakage.

SUMMARY OF THE INVENTION

The invention comprises a cannula pierceable, self-sealing gas-proofclosure for sealing an open end of a tube adapted to be air evacuated,which comprises; (a) a tubular body having (1) flexible, elasticsidewalls; (2) an open first end; and (3) a closed second end formed bya cannula pierceable, flexible, elastic end wall integral with saidsidewalls; and (b) a flange disposed radially about the periphery ofsaid sidewalls adjacent to said first end; said end wall having a convexinner surface and a concave outer surface when pressure on inner and onouter surfaces is equal.

The invention also comprises a method of inserting a cannula pierceable,self-sealing, gas-proof closure into an air evacuated tubular container,which comprises; (a) providing a tubular container having an open end;(b) providing a closure member which comprises, (1) a tubular bodyhaving flexible, elastic sidewalls, an open first end and a closedsecond end formed by a cannula pierceable, flexible, elastic end wallintegral with said sidewalls and (2) a flange disposed radially aboutthe periphery of said sidewalls adjacent to said first end; said endwall having a convex inner surface and a concave outer surface whenpressure on the inner surface equals the pressure on the outer surface;said closure member being of a dimension adapted to mate with the openend of said tubular container so that said sidewalls form a gas tightfrictional engagement therewith when inserted therein; (c) providing aninsertion tool which comprises a stiff elongated member having a memberfirst end and a member second end, said member first end being enclosedby a layer of a resilient material, said member first end and enclosinglayer together forming an insert end of a dimension such that wheninserted into the open first end of said closure member a frictionalattachment is effected between said insert end and said closure member;(d) inserting said insert end of said insert tool into the open firstend of said closure member so that the bore defined by the sidewalls andend wall of said closure member is substantially filled by said insertend and the insert end of said insert tool is attached to said closuremember; (e) evacuating air from said tubular container; (f) insertingthe attached closure member into the open end of said closure member;and (g) withdrawing the insertion tool from its attachment with saidclosure member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side elevation of an embodiment closure ofthe invention.

FIG. 2 is a cross-sectional side elevation of the embodiment of FIG. 1shown with insertion apparatus prior to insertion in an open end of atube container (the latter seen in fragmentary part).

FIG. 3 is a view as in FIG. 2 but at the start of insertion of theclosure member into the open end of the tube container.

FIG. 4 is a cross-sectional side elevation of the closure embodiment ofFIG. 1 but seen after complete insertion in the end of a tubularcontainer.

FIG. 5 is a cross-sectional side elevation of a preferred closureembodiment of the invention.

FIG. 6 is a cross-sectional side elevation of another embodiment closureof the invention.

FIG. 7 is a cross-sectional side elevation of still another embodimentclosure of the invention shown mounted in the end of a tubular container(the latter seen only in part).

FIG. 7A is a fragmentary view of the embodiment closure of FIG. 7showing a protective disc component added.

FIG. 8 is a cross-sectional side elevation of yet another embodimentclosure of the invention shown partially penetrated with a cannula.

FIG. 9 is a cross-sectional side elevation of another embodiment closureof the invention.

FIG. 10 is a cross-sectional side elevation of still another embodimentclosure of the invention shown upon initial insertion in a vacuumcontainer.

FIG. 11 is a cross-sectional view along lines 11--11 of FIG. 10.

FIG. 12 is a cross-sectional side elevation of another embodimentclosure of the invention.

FIG. 13 is an isometric view of a prior art tube holder.

FIG. 14 is a cross-sectional side elevation of a blood collectingcontainer employing a closure of the invention, mounted in the holder ofFIG. 13 and initially inserted in a blood vessel.

FIG. 15 is a view as seen in FIG. 14 but after a blood collection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

A complete understanding of the invention may be readily obtained by adescription of the preferred embodiments when read in conjunction withthe accompanying drawings of FIGS. 1-15, inclusive.

Referring first to FIG. 1, a cross-sectional side elevation of anembodiment closure of the invention there is seen closure 10 whichconsists of a tubular body formed of flexible elastic sidewalls 12 andend wall 14 which together define bore 16 which communicates to theatmosphere through open end 18. Disposed radially about sidewalls 12 andadjacent to the open end 18 and integral therewith is a thickenedportion serving as flange 20. Flange 20 serves to limit the insertion ofclosure 10 into an air evacuated tubular container as will be describedhereinafter in greater detail. Essential to closure 10 is theconcavo-convex end wall 14 closing end 22. More specifically, end wall14 as seen in cross-section has a convex inner surface 24 and a concaveouter surface 26. Inner surface 24 and outer surface 26 together withwall 14 describe a portion of a sphere or a dome. As shown in FIG. 1,the embodiment closure 10 has a bevel 28 on the sidewalls 12 at closedend 22, directed toward closed end 22. The bevel 28 facilitates assemblyof the closure 10 in an air evacuated tubular container as will bedescribed more fully hereinafter.

The closure 10 is a unitary one piece device molded of any flexible,elastomeric material conventionally used for fabricating gas-proofclosures. Representative of such materials are natural rubber(cis-1,4-polyisoprene, molecular weight 100,000 to 1,000,000),polyurethane elastomers, butyl rubber (copolymers of isobutylene anddiolefins) and the like. Preferred elastomeric materials are those oflow gas permeability such as butyl rubbers having a Shore A hardness ofcirca 35 to 80.

The dimensions of closure 10 may vary widely according to the dimensionof the opening to be sealed in the vacuum holding container. Thediameter of the tubular body, in the zone 5 just beyond the bevel 28(see FIG. 1), of closure 10 should be slightly larger than the insidediameter of the tubular container to be sealed so that the body portionis under compression when inserted into the tubular container. Thediameter of the tubular body above the bevel 28 may increase withproximity to the flange 20 so that the tubular body above bevel 28tapers or flares outwardly towards flange 20. In general, the thicknessof the sidewalls 12 and end wall 14 is considerably less than thedimensions of prior art closures for like openings. The thickness ofsidewalls 12 and end wall 14 should be such that they remain highlyflexible but bear structural integrity. As an example of dimensionswhich may be employed in a closure 10 having a height of about 0.612inches and an average diameter (exclusive of flange 20) of about 0.487inches, sidewall 12 may have a thickness of about 0.909 inches. In thisinstance, end wall 14 may have a thickness of about 0.040 to 0.090inches. Those skilled in the art will appreciate the significance andadvantages of these very thin structural walls, in comparison to priorart closures used for the same purpose and which were heretofore notpossible. As shown in FIG. 1, the embodiment closure 10 has a flangeheight of about 0.187 inches and a thickness through the flange area ofabout 0.143 inches. The bevel 28 preferably is at an angle of about 60°to the plane normal to the longitudinal axis of closure 10. A closure 10of the above dimensions will have a weight saving over the bulkier priorart closures of similar size, of about 30%. The relatively thin wallconstruction of the closure 10 is less costly in terms of material costand permits easier insertion in a vacuum container. The latter advantageresults from the easier deformation of the closure 10 during insertion,requiring less force for insertion. In use, the closure 10 may bepierced by a needle or cannula thrust through the self-sealing end wall14 when access to the enclosed area beneath the closure, mounted in atubular container, is desired. Upon withdrawal of the needle or cannula,the self-sealing wall 14 closes the entry point to maintain enclosure.

The method of the invention is carried out by providing a closure of theinvention such as closure 10, a tubular container having an open end andan insertion tool of specific structure. Referring now to FIG. 2, across-sectional side elevation of the embodiment closure 10 about to beinserted in the open end 30 of a tubular container 32 (seen in part),there is seen insertion tool 34 partially inserted in bore 16 of closure10 so as to frictionally engage and hold closure 10. Insertion tool 34comprises an elongate rigid member 36 which may be for example a rod ofmetal or rigid plastic resin. Member 36 should be stiff enough towithstand a force along its axis of at least 10 lbs., without bending.One end of the member 36 may be a handle (not shown) for manualoperation or for attachment to the piston of an automatic ram setmachine for automatic insertion of closure members. The other end ofmember 36 is enclosed by a layer of a resilient material 38 which iscompressible. Resilient material 38 may be, for example, a foam rubber,a flexible synthetic resin foam or the like. Preferably, the resilientcompressible material 38 will have a durometer hardness of circa 30. Theresilient material 38 and member 36 together comprise an insert end or"finger" for handling and holding the closure 10 and directing itsinsertion in the open end 30 of tubular container 32. Bevel 28 aids indirecting the insertion. The closure 10 is inserted under force of tool34 in a vacuum chamber (not shown) so as to air evacuate tube container32 prior to insertion. During initial stages of insertion, elongatemember 36 carries the resilient compressible layer 38 into the bore 16of closure 10 so as to substantially fill bore 16 and so as to givesupport to sidewalls 12 and end wall 14 during the insertion process(see FIG. 3). Those skilled in the art will appreciate that the tool 34need not be constructed so compressible layer 38 fills bore 16 of theclosure 10 to be inserted in a tube 32. To facilitate insertion of thetool 34 into bore 16 it may be preferable to use a relatively smallsection of compressible material 38 so that only a portion of the bore16 is filled with compressible material 38. In FIG. 3, initial insertionof closure 10 has been effected. Due to the fact that sidewalls 12 arerelatively thin and flexible and insert end layer 38 is readilycompressed, the closure is easily inserted in an air evacuated tubecontainer 32 with a minimum of required force. The sidewalls 12 willflex inwardly vary easily to overcome the resistance of insertion intothe smaller diameter tube 32. After complete insertion up to flange 20,the insertion tool 34 is easily removed leaving the closure 10 in placeas shown in FIG. 4, a cross-sectional side elevation of the closure 10mounted to hermetically seal air evacuated tube container 32. Theclosure 10, thus mounted, will sustain and hold the vacuum in container32 even though closure 10 have relatively thin, flexible sidewalls 12and end wall 14 because of the concavo-convex configuration of end wall14 in conjunction with the relatively flexible sidewalls 12.

More specifically, and as illustrated by the arrows in FIG. 4, thepressure differential (atmosphere to tube vacuum) helps create a tighterseal between closure 10 and tube 32 than can be accomplished by simplecompressive force alone as is the case with prior art closures. Inaddition to pressure differential forces which help seal and hold theclosure in place, there exists a new radial force not present in priorart closures. The radial force is induced by the radial outward motionfrom the center of wall 14 along the axis of end wall 14 to theperiphery thereof. This outward force results from the higher pressureon the upper surface 24 of end wall 14 as compared to the lower pressure(vacuum) exerting itself upon lower surface 26. The pressuredifferential flexes end wall 14 to flatten the concavo-convexconfiguration thereby creating the radial force directed toward theperiphery of end wall 14. Since the force is concentrated in the lowersolid portion of the closure, in the area of end wall 14, a powerfulrestraining and sealing force against tube 32 is obtained due to theflexibility of sidewalls 12. This additional sealing force not found inprior art closures enhances the hermetic seal between closure andcontainer. In the absence of the concavo-convex configuration of endwall 14, the sidewall 12 would actually pull away from the walls ofcontainer 32 and closure 10 would be drawn into the container 32 by thevacuum force. The long term preservation of vacuum in container 32 isalso enhanced and rendered more positive since stress relaxation of theelastomeric material (compression set) is not a factor in obtaining thehermetic seal obtained with use of closure 10. The radial sealing forcealso provides increased resistance to accidental removal of closure 10during needle withdrawal after use as will be described in greaterdetail hereinafter.

A further advantage in the closure member 10 of the invention resides inthe visual indication it provides as to the state of the vacuummaintained in tubular container 32. As described above, the pressuredifferential on surfaces 24 and 26 of end wall 14 causes a flatteningout of the concavo-convex configuration of end wall 14. If there is aloss of vacuum in the container 32, the natural arc of theconcavo-convex configuration will return with the equalization ofpressures on surfaces 24 and 26. This return of an arc is observable andan indication to personnel that vacuum has been lost in container 32.Those skilled in the art will appreciate many refinements possible todetermine the degree of vacuum loss, i.e.; simple measurement of bore 16depth, or mechanical and optical means of measurement of the convex arcare possible.

Referring now to FIG. 5, a cross-sectional side elevation of a preferredclosure of the invention, there is seen closure 40 which is essentiallythe same structure found in closure 10 of FIG. 1 but with the additionof a protective cap 42 adhesively attached to end 22 so as to cover theouter surface 26 of end wall 14 and bevel 18 surface. Cap 42 isolatesclosure 40 from the contents of the container in which it is emplaced,obviating the possibility of any interaction between the containercontents and the closure 40. For example, if the container 32 is to beemployed in the collection of blood, additives such as oxalates orcitrates, conventionally added to such containers, are prevented fromclinging to the elastomeric closure 40 by the interposition ofprotective cap 42. Protective cap 42 is preferably of a syntheticthermoplastic resin material which is stable when sterilized by wet ordry heat. Representative of such materials are polypropylene, highdensity polyethylene, polytetrafluoroethylene and the like. Preferred asthe material for fabricating cap 42 is polytetrafluoroethylene becauseof its extremely high cold flow properties and its resistance toattachment of fibrin or red blood cells which might otherwise attach tothe closure 10 when the container is to hold blood specimens. It isimportant that the cap 42 be firmly secured to the end wall 14 so as notto separate therefrom and be loosely deposited in the vacuum holdingcontainer. In the closure 40, a polytetrafluoroethylene cap 42 having athickness of circa 0.015 inches makes contact with the inner walls ofthe container to be closed, along its peripheral edges 44. When closure40 is mounted in the opening of an air evacuated tubular container, theedges 44 of cap 42 are forced against the inside container tubular wallsby virtue of the action of the domed end wall 14 as described above.This results in a very high sealing pressure. It is important to notethat peripheral edges 44 do not interrupt a substantial surface contactbetween the sidewalls 12 and the interior walls of the tubular containerin which closure 40 will be mounted. The substantial elastomer-containercontact offers primary resistance to accidental fallout of the closure40, providing tight frictional engagement of the closure 40 with thecontainer. The high sealing pressure coupled with the high cold flowproperty of polytetrafluoroethylene creates an intimate and absoluteseal enhancing the hermetic seal of the closure 40 and isolating theelastomeric material of closure 40 from contacting the containercontents. In addition, as previously described, the new radial forcefound in the closures of the invention caused by differential pressure,provides for a new radial sealing force caused by the radial "rolling"action of the disc 42 edge 44 against the inner wall of the container inwhich the closure 40 is mounted. This provides for a very secure, liquidseal while not interfering with the hermetic seal formed by theelastomer body sidewalls 12 with the container body.

Referring now to FIG. 6, a cross-sectional side elevation of analternate embodiment enclosure of the invention, there is seen a closure41 which differs from closure 40 in FIG. 5 only in respect to thestructure of end cap 41. End cap 41 as seen in FIG. 6 may be fabricatedfrom the same materials employed in the fabrication of end cap 42. Endcap 41 differs in that it has a skirt portion 46 which is of a dimensionadapted to permit nesting in the open end of a tubular container priorto insertion of the closure member 41 therein. Skirt portion 46 which isintegrally molded with cap 41 is a convenience in assembling closure 41into the open end of an air evacuated container. The skirt 46 is of adimension slightly less than the internal diameter of the tubularcontainer so that closure 41 may be set up initially on the mouth ororifice of the container and later inserted as described above, i.e.;with the aid of an insertion tool 34. In a preferred embodiment, skirt46 will have one or more slots 48 therein to facilitate the airevacuation from the tubular container after the closure 41 is set on themouth of the tubular container but before insertion therein.

As shown in FIG. 1, a cross-sectional side elevation of a furtherembodiment closure of the invention, there is seen a closure 50 whichis, essentially, a closure 40 as described above and shown in FIG. 5 butwith an added puncture diaphragm 52 secured (preferably bonded) to theflange 20 by a relatively stiff ring 54. The ring 54 may be a metal orplastic ring and contacts only the closure 50. The ring 54 also supportsand stiffens the puncture diaphragm 52. Diaphragm 52 covers and sealsbore 16 closed to prevent the collection of contaminants therein such asdirt, dust, foreign objects and the like which might be carried throughthe pierceable end wall 14 upon puncture with a cannula or needle. Thepuncture diaphragm 52 also serves to wipe a cannula or needle uponwithdrawal, thereby wiping any droplets of fluids from the needle. Thisis particularly advantageous when the fluid concerned may be hazardousto operating personnel. The wiped drop or droplets of material fluidsare retained in bore 16 upon withdrawal of the cannula through puncturediaphragm 52.

FIG. 7 also shows the close hermetic seal effected between protectivecap 42 at end 44 with the interior wall of tubular container 32. Asdescribed above, the vacuum within container 32 in conjunction with theatmospheric pressure upon surface 24 of end wall 14 causes theconcavo-convex configuration to flatten out and force protective capends 44 (lining the bevel 28) with very high pressure against thetubular container 32 walls. Those skilled in the art will alsoappreciate that the relatively thin concavo-convex end wall 14facilitates needle penetration when access to the contents or space ofcontainer 32 is desired. Not only is the end wall 14 relatively thin incomparison to prior art closures for hermetically sealing tubularcontainers, but the concavo-convex configuration in conjunction with thefact that it is under stress when mounted in a vacuum holding container32, causes greater crack growth upon penetration with a needle, allowingfor easier penetration. The radial force exerted by the concavo-convexconfiguration of end wall 14 also secures the closure 10 in place duringwithdrawal of the needle. The diaphragm 52 shown in FIG. 7 alsofunctions to position and hold a veni-puncture needle prior to itspiercing the end wall 14. FIG. 13 shows a conventional veni-punctureneedle and holder of the prior art. The assembly comprises a doubleended piercing cannula 86 mounted in the closed end 88 of a tubularholder 90 so that needle end 92 is centered within holder 90 and needleend 94 is outside of holder 90 and encased by sheath 96. In initial use,a tubular container 32 closed by a closure 50 is inserted in the openend 98 of holder 90 and seated on the needle end 92 by needle end 92piercing the diaphragm 52 as shown in FIG. 14. FIG. 14 shows the needleend 92 resting in bore 16 and the still closed vacuum container 32 heldin its position by the frictional forces between needle 86 and diaphragm52. With container 32 thusly secured, the operator may unsheath needleend 94 and use that end to accomplish a veni-puncture. A shown in FIG.14, the initial blood flow upon veni-puncture is into bore 16. Theoperator, when ready to collect a blood specimen in container 32 thenmoves the container 32 further into holder 90 so needle end 92 willpierce end wall 14 and enter the vacuum chamber of container 32 as shownin FIG. 15. When the desired amount of blood has been collected incontainer 32 as shown in FIG. 15, the veni-puncture is closed bywithdrawal of needle end 94 and container 32 may then be withdrawn fromholder 90 to seal the blood specimen collected in container 32. Theinitial blood flow received in bore 16 is also sealed by theself-sealing diaphragm 52 which also functions to wipe the needle point92 free of any residual blood droplets as it is withdrawn through thediaphragm 52. This sealing of bore 16 and wiping of needle point 92assures that blood is not spilled into the vicinity of the operator orthe patient. This is particularly valuable if the blood is or poses ahealth hazard by open spilling into the environment.

An advantage of the above described procedure is that it frees theoperator from having to juggle a loose collection container and/or spillblood unnecessarily in the vicinity of the patient while collecting aspecimen.

FIG. 7A is a cross-sectional side elevation of a fragment of closure 50as shown in FIG. 7 with the addition of a removable disc 53 held inplace over diaphragm 52 by ring 54. The removable disc 53 serves topreserve the sterile condition of a diaphragm 52 and surface 24 prior toneedle insertion. Alternatively, the removable disc 53 may be usedwithout a puncture diaphragm 52 to protect bore 16 and surface 24 fromcontamination prior to insertion of a needle through the closure 10. Thedisc 53 may be stripped off prior to use by pulling the tearable fingergripping surface 55.

Referring now to FIG. 8, there is seen a cross-sectional side elevationof another embodiment closure 60 of the invention. Closure 60 isessentially a closure as seen in FIG. 7 but without protective cap 42and with a different puncture diaphragm member. In closure 60 of FIG. 8,the puncture diaphragm 56 consists of a cylinder of absorbent materialsuch as a polyurethane foam. The closure 60 is advantageous in haltingthe flow of materials through needle 58 after it has been withdrawn froma tubular container (in which closure 60 is mounted) or prior toinsertion through end wall 14 (but after veni-puncture) to preventpremature blood transfer. More specifically, needle 58 is initiallythrust through puncture diaphragm 56, through bore 16, through end wall14 and into the vacuum space of the tubular container (not shown in FIG.8). The cannula thus entered may bear fluids into the vacuum holdingcontainer. Upon withdrawal of the cannula 58, it may be positioned sothat its end terminates in puncture diaphragm 56. Puncture diaphragm 56being an absorbent material will stem continued flow of fluids throughneedle 58 until such time as the other end may be disconnected from thefluid source.

Referring now to FIG. 12, a cross-sectional side elevation of apreferred closure 60 is seen, with analagous parts numbered as in FIG.8. The closure of FIG. 12 differs from that of FIG. 8 in that thediaphragm 56 fills bore 16, obviating the need for ring 54. Thediaphragm 56 is advantageously flexible so as not to interfere with theaction of endwall 14 as previously described.

FIG. 9 is a cross-sectional side elevation of another embodiment closure70 of the invention which differs from the closure 10, 40 and 41described above in that the bore 16 is closed and protected fromcontamination by a strip 72 of pressure sensitive tape of a removablesheet of a polymeric resin. The strip 72 may be peeled off when entrythrough the closure 70 with a cannula is desired.

FIG. 10 is a cross-sectional side elevation of still another embodimentclosure 80 of the invention shown being initially inserted in a tubularcontainer 32. The closure 80 differs from closure 10 seen in FIG. 1 inthat a plurality of grooves 82 are cut in sidewalls 12, in the directionof the vertical axis of the closure 80. The grooves 82 facilitate theinsertion of the closure 80 into the tube 32 by reducing the frictionalforce to be overcome between tube 32 and closure 80 and also allows theescape of an air remaining in tube 32 which will be displaced by theclosure 80. The relationship of the grooves 82 can be seen in greaterdetail by referring to FIG. 11, a cross-sectional view along lines11--11 of FIG. 10.

Those skilled in the art will appreciate that many modifications may bemade to the article and the method of the invention without departingfrom the spirit of the invention. For example, any closure of theinvention may be inserted in a tubular container with the aid of asimple metal or plastic push-rod. As a further example, the closuresdescribed above may be fabricated in any desired size. Preferablyhowever, the diameter of the closure will bear a relationship to theheight of the closure within the ratio of from about 0.8:1. Thispreferred ratio assures maximum sealing effect from the structure of theclosures of the invention.

What is claimed:
 1. A cannula-pierceable, self-sealing, gas-proofclosure for sealing an open end of an air evacuated blood collectiontube, which comprises;(a) a tubular elastomeric body having(i) flexible,elastic sidewalls; (ii) an open first end; and (iii) a closed second endformed by a cannula pierceable, flexible, elastic end wall integral withsaid sidewalls; and (b) a flange disposed radially about the peripheryof said sidewalls adjacent to said first end; said end wall having aconvex inner surface and a concave outer surface when pressure on innerand on outer surfaces is equal, said tubular body having a diameterwhich bears a ratio to the height of the body of about 0.8:1 and to thethickness of the second end of from 5.4:1 to 12.1:1; whereby when theclosure is emplaced in and sealing an open end of an air-evacuated tube,the higher pressure on the convex inner surface of the end wall ascompared to the lower pressure (vacuum) exerting itself on the concaveouter surface creates a pressure differential on the end wall, flexingand flattening the concavo-convex configuration and creating a radialforce directed toward the periphery of the end wall, said forceaffecting a restraining and sealing force between the closed second endof the elastomeric body and the air-evacuated tube.
 2. The closure ofclaim 1 wherein said tubular body is cylindrical.
 3. The closure ofclaim 1 wherein said second end has a smaller diameter than said firstend.
 4. The closure of claim 3 wherein the sidewalls at said second endare bevelled toward said second end.
 5. The closure of claim 1 whereinsaid body is fabricated from butyl rubber.
 6. The closure of claim 1wherein said flange is an integral part of said sidewalls.
 7. Theclosure of claim 1 wherein said body is molded from an elastomericmaterial selected from natural rubber, polyurethane and butyl rubber.